MT (Mechanically Transferable) ferrules are widely used for collectively connecting multi-fiber cables. Japanese Patent Application Laid Open No. 2008-026647 (published on Feb. 7, 2008, hereinafter referred to as Literature 1) describes a configuration in which an MT ferrule attached to a terminal end of a multi-fiber cable is connected to an MPO (Multi-fiber Push On) optical connector plug incorporating an MT ferrule at its front end through an optical receptacle housing.
FIG. 1 illustrates an MT ferrule and an optical receptacle housing described in Literature 1. An MPO optical connector plug is omitted from FIG. 1. FIG. 2 illustrates a configuration of the optical receptacle housing. Shown in FIG. 1 are the MT ferrule 11, a multi-fiber cable 12, an optical module 13, and a guide pin 14 inserted in the MT ferrule 11. FIG. 1 illustrates the MT ferrule 11 before being housed in the optical receptacle housing 20.
The optical receptacle housing 20 is a combination of a ferrule receiving part 21 receiving the MT ferrule 11 and a plug receiving part 22 in which an MPO optical connector plug is inserted and connected. The ferrule receiving part 21 includes a cylindrical ferrule receiving main body 24 defining a ferrule receiving hole 23 and a flange 25.
A pair of hooks 26 extending toward the optical module 13 is provided in the upper and lower walls of the ferrule receiving main body 24 so that the MT ferrule 11 inserted in and set in the ferrule receiving part 21 is latched and held by the hooks 26.
FIG. 3 illustrates a structure interconnecting a backplane (backboard) on which optical fibers are installed and a board (daughter board) that is described in Japanese Patent Application Laid Open No. 2007-102013 (issued on Apr. 19, 2007, hereinafter referred to as Literature 2).
A plurality of optical fibers 32 are arranged into a sheet-like structure and affixed to the backplane 31. An end portion of the optical fibers 32 is bent so that the optical fibers 32 are substantially perpendicular to the main surface of the backplane 31, and an optical connector 33 is attached at the end portion.
Optical connectors 35 to be optically connected to the optical connectors 33 are provided at an end of a board 34. The optical connectors 35 and photoelectric conversion modules 36 on the board 34 are interconnected through an optical fiber array 37.
In this example, five boards can be attached to the backplane 31. Four optical connectors 35 are attached on the board 34 illustrated in FIG. 3, which are to be connected to four optical connectors 33 on the backplane 31. The optical fibers in each optical connector 33 on the backplane 31 are arranged in parallel to the plane of the board 34 and, likewise, the optical fibers at the end portion of the optical fiber array 37 are arranged in parallel to the plane of the board 34. In this example, the four optical connectors 35 on the board 34 illustrated and the four optical connectors 33 on the backplane 31 to be connected to the optical connectors 35 are arranged in the direction of the long sides of their front end faces.
Literature 2 does not describe in detail a structure for attaching the optical fibers 32 to the optical connectors 33, for example. Furthermore, the depicted structure that connects board 34 to the backplane 31 uses four optical connectors 33, 35 for each boards.
In order to reduce the number of parts, save optical connectors installation space, and increase the packing density, an MT ferrule could be attached to the terminal ends of a multi-fiber cable and a (large) number of MT ferrules could be set in one connector housing to unify optical connectors into one.
Such a configuration needs only one optical connector to be attached to a backboard for connecting one daughterboard. In this case, a plurality of MT ferrules are preferably arranged in the direction of the long side of the front end faces of the MT ferrules. That is, MT ferrules are preferably arranged in the direction in which the optical fibers are arranged in the front end faces of the MT ferrules. This arrangement is the same as the arrangement of the four optical connectors 33 corresponding to the optical connectors 35 on the board 34 in FIG. 3. The reasons why the arrangement is preferable lie in easiness of installation of multi-fiber cables on the backboard and accessibility to the terminal ends of the multi-fiber cables in consideration of board space saving.
In order to enable an MT ferrule to be easily attach to a connector housing, it is desirable that a mechanism, such as hooks 26 depicted in FIGS. 1 and 2, that latches and holds the MT ferrule be provided. The pair of hooks 26 in FIGS. 1 and 2 holds the long side of a rear end flange 15 of the MT ferrule 11. MT ferrules are typically mated and unmated by grasping the flange with fingers. With the structure in which the pair of hooks 26 holds the long side of the flange as described above, the MT ferrule is mated and unmated by grasping the short side of the flange.
Therefore, if a plurality of MT ferrules are arranged in the direction of the long side of the front end faces of the MT ferrules (the direction of the long side of the flange), the MT ferrules need to be spaced a sufficient distance apart from one another so that an adjacent MT ferrule does not obstruct grasping the short side of the flange. This increases the size of the connector housing that houses the plurality of MT ferules, preventing size reduction of optical connectors.